DropzoneJS is an open source library that provides drag’n’drop file uploads with image previews. Plugin page. 

<!-- Css --><link rel="stylesheet" href="vendors/dropzone/dropzone.css" type="text/css"><!-- Javascript --><script src="vendors/dropzone/dropzone.js'"></script>
Basic Demo

The typical way of using dropzone is by creating a form element with the class 

<form action="/file-upload" class="dropzone">  ...</form>